[JAVAee]spring-Bean对象的执行流程与生命周期

执行流程

spring中Bean对象的执行流程大致分为四步:

启动Spring容器
实例化Bean对象
Bean对象注册到Spring容器中
将Bean对象装配到所需的类中

①启动Spring容器,在main方法中获取spring上下文对象并配备spring.

import demo.*;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class Test {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");}
}

②实例化Bean对象,spring根据配置文件中的路径搜寻"demo"包中含有注解的类.

通过这些类实例化出Bean对象,并对他们进行初始化Bean对象的属性,

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:content="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"><content:component-scan base-package="demo"></content:component-scan>
</beans>

③将实例化出的Bean对象注册到Spring容器当中.

@Component
public class UserBean {private String name;@Bean(name = {"user","wualala"})//Bean方法注解,将方法返回的对象存储到spring中变成Bean对象public UserBean userBeanMethod(){UserBean userBean = new UserBean();userBean.name = "wow";return userBean;}

④Bean对象的使用,将其分配到所需的类中

@Controller
public class UserController {@Resource(name = "user1")//@Autowiredprivate UserBean userBean;public UserBean getUserBean() {return userBean;}
}